High pressure steam turbines are typically constructed of top and bottom halves that are joined at a horizontal flange joint. In order to securely maintain the seal at the flange joint, large diameter bolt assemblies are provided at axially spaced locations along the flange joint. Such bolt assemblies comprise heavy components, including a heavy lower nut that is removed from a threaded shaft of the bolt assembly to permit separation of the top half from the bottom half or, alternatively, that is installed onto the lower end of the threaded shaft of the bolt assembly during assembly of the casing halves.
The lower nuts for the bolt assemblies may weigh in the range of 15 to 90 pounds, such that a heavy lower nut typically requires an overhead crane to facilitate removal and installation. Hence, the removal/installation of the bolt assemblies, such as for turbine maintenance, requires scheduling of valuable crane resources within the turbine facility, and may increase the downtime of the turbine in the event that a crane is not readily available.